This invention relates to a rotary piston pump for semi-solid products. This invention relates more particularly to a rotary piston pump for minced meat, in particular for producing sausages or the portioning of minced meat comprising large pieces of muscle.
In the field of producing sausages, piston pumps are known in the art comprising a stator defining a cylindrical cavity, a rotor or barrel housed in said cylindrical cavity, able to be driven in rotation by the shaft of a motor, said rotor comprising an array of bores positioned axially and spaced circumferentially, wherein are mounted pistons, a mechanical cam cooperating with the pistons in order to provoke an alternating back and forth movement of said pistons between a low position and a high position during the rotation of the barrel, a lid closing the cylindrical cavity and comprising a feeding orifice coming into communication with at least one cylindrical chamber formed by the barrel cylindrical bore and a piston associated therewith, and intended to be in communication with a hopper, and a discharging orifice able to come simultaneously into communication with at least two consecutive cylindrical chambers. In order to facilitate the filling of the cylindrical chambers, it is known in the art to apply a vacuum from the top in the cylindrical chambers, when the pistons are in low position, by the intermediary of a vacuuming orifice provided on the lid. In pumps of similar design, the pistons are housed in radial chambers and the feeding and discharging orifices are formed on the stator.
The minced meat output from such pumps maintains its qualities. However, such pumps do not make it possible to obtain at the output a constant flow of products, despite various adjustments made to the form of the discharging orifice and of the mechanical cam. The weight of the sausages obtained with these pumps can vary by 10 to 15% in relation to the desired average weight. In order to be sold, it is necessary to guarantee a substantially constant unit weight corresponding to the announced weight. The producer is therefore obliged to increase the desired average weight in order to be sure that the announced weight is reached. These pumps therefore are not widely used today due to the considerable loss of products for the producer.
Vane pumps have been proposed as a replacement for these piston pumps. Such vane pumps provide a substantially constant flow. However, the meat undergoes major flaking and high pressure which results in heating the meat and the fat of the meat thus heated tends to spread out. At pump output, the meat is completely denatured and has a whitish aspect.
The purpose of this invention is to overcome the aforementioned drawbacks by proposing a pump that provides a substantially constant flow at output, while still preserving the quality of the minced meat.